U.S. airlines are monitoring the investigation of the fatal plane crash in Indonesia on Monday, which involved a Boeing 737 Max 8 aircraft that’s been pegged as a future workhorse for fleets at Southwest, American and other carriers around the globe.

Lion Air Flight JT610 crashed into the waters of the Java Sea near Jakarta shortly after takeoff with 189 people on board. Officials Monday indicated no survivors are expected.

The investigation into the crash was still in its early stages Monday and no cause for the accident has been identified.

Third-party flight tracking data showed an unusual ascent at varying speeds during the early minutes, Bloomberg News reported. The data showed the aircraft plunged toward the ocean at more than 300 miles per hour in its final moments, as much as 15 times faster than a typical descent.

The accident is the first for the 737 Max 8, the latest version of Boeing’s popular narrowbody aircraft which entered service in 2017.

Boeing said it has received 4,700 orders for Max aircraft, which come in multiple versions based on their size, from more than 100 customers around the world. Boeing said Monday it's providing technical assistance to accident investigators.

The aircraft incorporates next-generation engines and other features that make it the quietest and most fuel efficient version of the jet yet, with airlines banking on the model to play a key role in their fleets for decades to come.

Southwest Airlines was the first to operate the Max 8 in the United States when it put the aircraft into service in October of last year. The Dallas-based airline has 23 Max 8 aircraft in its fleet as of Sept. 30 and is slated to take nine more deliveries this year.

Southwest has firm orders for 227 of the aircraft, which have a list price of $117 million each.

“The entire Southwest family extends our Southwest heart to Lion Air and offers our deepest condolences to each of the families and loved ones affected by the tragic accident in Indonesia,” the company said in a statement. “We are in touch with Boeing and will closely monitor the situation and any findings from this tragic event. Currently, our MAX fleet remains fully operational with no adjustments to our schedule.”

Fort Worth-based American Airlines has taken delivery of 15 737 Max 8s out of its total order for 100 of the aircraft.

“American Airlines extends our condolences to the families and friends of those on board Lion Air 610,” the company said in a statement. “We continue to closely monitor the investigation via Boeing and the National Transportation Safety Board.”